Re: how can I change my storage into sd card in galaxy core 2?
If you go into the Application Manager and an app that you select shows the MOVE TO SD option, you can, but you can't change the default storage path. Every app will go to your internal memory first.
Also, remember that even apps that let you move to SD, don't move everything. The main APK file will always be on your phone's internal memory, and it's up to the dev to decide what can be moved to SD card (usually just external downloads or game saves).
If you root and apply a hack to your phone, though, you can simulate the SD Card as part of your internal memory. But given the fact that SD cards are not that reliable, it's not something I'd recommend.